Recently, a nitride semiconductor light emitting device, a light emitting device capable of generating light having a wide range of wavelength bands, including monochromatic light such as blue, green, or the like, has come to prominence in relevant technical sectors in which it may be applied to a backlight unit (BLU), an electronic device, a general illumination device, or the like, beyond the existing simple display or portable liquid crystal display markets.
As the purposes of nitride semiconductor light emitting devices have been diversified, currents applied thereto have also been diversified. A mobile phone is operated with a low applied current of about 20 mA, and as nitride semiconductor light emitting devices have increasingly been used as high output light emitting devices in BLUs and general illumination devices, currents applied thereto have varied from 100 mA to 350 mA or more.
The increase in strength of currents applied to nitride semiconductor light emitting devices has led to an increase in current density of the light emitting devices, and in the case of nitride semiconductor light emitting devices based on InGaN/GaN, internal quantum efficiency has sharply reduced as the density of applied currents has increased. Thus, in order to address this problem, there have been attempts to introduce a current spreading layer between an n-type nitride layer and an active layer to enhance electron spreading efficiency in a horizontal direction to thus increase internal quantum efficiency.
However, strain increases due to a difference in lattice constants. Thus, an influence of a piezoelectric field effect has increased which significantly degrades quantum efficiency in an active layer.
Accordingly, there exists a need for further improvements in semiconductor light emitting devices which include a current spreading layer capable of minimizing an influence of a piezoelectric field effect and improving forward voltage characteristics and/or luminous efficiency.